FHB House Framing in Pictures — Roof System
Gussets and 2x4s make a deep-sloped ceiling for a thick layer of insulation.
When it comes to framing the roof, Paul and Tim Biebel aren’t wed to any one method. For their production spec houses they compare the cost of stick framing to trusses and let cost dictate the choice. Because of the shape of this particular roof, stick framing was much cheaper. In order to have at least R-60 of dense packed cellulose in the sloped ceiling they frame the roof in a way that’s reminiscent of the double studs walls by using 2×12 rafters that are furred down to create extra depth.
Click through the slideshow to see each step in the roof framing process.
While waiting for the crane to help them set the ridge beams the crew cut all of the 2×12 rafters.
In preparation for setting the rafters the sheathing along the eaves is notched at each rafter location. They’ve run the sheathing long, past the top plate so the Zip System sheathing can serve as continuous blocking between the rafters. Cutting the notches is faster than nailing blocking in place between each rafter.
The sheathing is stopped 3/4 in. below the roof sheathing to allow for soffit venting.
The engineer specified a structural ridge–in this case Weyerhaeuser’s 3.5 in. x 16 in. Eastern Parallam PSL beam. Two 6×6 Parallam PSL posts–one on each side of the stairs–transfer the load to the foundation.
With the ridges set the end rafters are nailed in place. The temporary support at the gable end will be removed later.
Working toward the middle, all of the long rafters are set in just a few hours. Then the valleys are framed.
With the rafters in place the Zip System sheathing and tape will sheath the roof and dry it in.
Once the sheathing panels are nailed off the crew works their way around the roof taping all the seams and the roof is dried in.
Because the sloped ceiling will be dense-packed the ventilation channel must be robust: cheap Styrofoam ventilation baffles won’t stand up to the pressure. The crew building the ProHOME build the ventilation channel on site. Ripped-down 1×3 strapping is stapled to each side of the rafter to serve as nailers for an OSB baffle.
The nailers provide a 3/4-in. gap between the roof sheathing and OSB baffles stapled to the nailer. The OSB withstands the dense-packed insulation. The ventilation channels extend beyond the level of loose-fill cellulose in the attic.
All edges of the ventilation channel are sealed with Titebond’s X-treme Foam.
To fur down the rafters a chalk line is snapped on the rafter collars 20 in. from the sheathing. A 2×4 is tacked in place at this line and 20 in. in from the sheathing at the top plate. OSB gussets are nailed to the rafters and to the 2×4 to stiffen and straighten them. In the photo a straight edge is used to ensure the ceiling will be flat.